The £15 billion-dollar Crossrail that will cover nearly 32 miles of underground track is now complete.

But those eager to use it will have wait a little while longer.

Transport Secretary Chris Grayling was on hand this week to install the final piece of the Crossrail track that will be partly operational next year.

"The Elizabeth line will transform rail transport in London with better and faster journeys for passengers and the official completion of the track is a hugely significant milestone towards delivering this scheme on time and within available funding," Mr Grayling said.

"But this isn't just a success story for London.

Crossrail, Europe's biggest construction project, has created jobs and driven economic growth across the UK with companies based here winning 96 per cent of the scheme's contracts."

Trains will run on the line under London from December next year, linking Reading and Heathrow, with services connecting Essex beginning in December 2019.

London mayor Sadiq Khan said: "The completion of the Elizabeth line track is a huge milestone on the way to finishing a project that will transform transport across London and the south east.

"With brand new trains and step-free stations, the Elizabeth line will provide a truly world-class service for passengers, and this important landmark is testament to the hard work and expertise of all the men and women who have been working on the project."